It would seem that Calgary is losing its 777 to fulfil the last link in the aircraft shuffle equation.
MAN-JFK axed, its 767 moves to LHR to operate LHR-YYC
LHR-YYC downgraded from 777 to 767 to provide 777 to LGW-JFK
LGW-JFK started using YYC 777 from LHR
Ta Da...